A number of fasteners have been used in the past for securing or suspending articles on hollow walls, such as, for example, dry walls or plasterboard walls. These walls are thin and produced out of powdery materials so that conventional fasteners, such as screws, nails, etc. are ineffective in supporting all but the lightest of articles hung on the wall. Through the years, the solution adopted to provide secure support for articles on such hollow walls has been the use of two part supports comprising a combination anchoring member and a conventional fastening member such as screw or bolt which is secured to the anchoring member, once such member has been inserted in and through the hollow wall. Typical such prior art fastening supports or anchors are described in the patent art, exemplified by U.S. Pat. Nos. 1,169,635, 1,181,336, 1694,493, 3,005,645, 3,170,361, 4,074,941, 4,500,238, 4,704,057, 4,997,327, 5,412,848 and 5,417,531, among others.
These various fastening members are inserted into the hollow wall usually by first drilling a hole through the wall sufficient to allow for insertion of the anchoring member in the hole. Once the anchoring member is in place, a screw or bolt is employed to either expand a portion of the anchoring member in the wall or to deform the anchoring member behind the wall so as to provide a back up plate-like arrangement to spread the weight of an article hung on the wall over a larger surface area. In both instances, the anchoring member becomes, for all practical purposes, a permanent part of the wall, as removal is difficult and results in damaging the wall.
Thus, while there are various types of wall anchor devices, the two types that are most common are a molly type anchor device and a toggle-type anchor device. A molly type anchor device generally consists of a body which is inserted through an opening formed in the drywall. The body threadably receives a screw, which when threaded into the body, causes the body to be compressed against the inner surface of the hole formed in the wall. The compression of the body results in deformation, wherein portions of the body spread out, pressing against the material defining the hole and possibly over the inner surface of the drywall. This prevents withdrawal of the body, and firmly anchors the device to the wall. Toggle type anchor devices consist of wings spread by a spring. The wings are forced together and inserted through an opening formed in the wall. Once through the wall, the wings are expanded or toggled apart by the spring. As the screw is threaded through the wing assembly, the wing assembly is pulled firmly against the inner surface of the wall. Most if not all commercially available toggle devices cannot be removed from the wall once installed, since there is no apparatus or practical procedure for closing the wing to allow withdrawal from the opening in the wall.
In the case of the aforementioned toggle type anchor devices, there is usually some kind of pivot nut intercoupling structure to enable the operating screw to move the toggle arms pivotally from a collapsed position to an expanded position. Generally the entire operating screw mounting load imposed on the fastening device or anchor is carried by this pivot structure. Thus, the strength of the toggle bolt is determined almost solely by the strength of the small inter-coupled elements rather than the overall structure of anchor itself. Also, since the weight of the load to be supported by the toggle anchor is applied to the toggle operating screw itself, the weight or load carrying capacity of the anchor is likewise limited by the strength of the toggle arm pivot structure, which is usually the weakest link in the anchoring system. In addition, if a present day type toggle operating screw or bolt is removed, the toggle arms that form the nut portion of the anchor will fall in the space behind the blind side of the wall. Therefore, a new toggle arm nut structure must be provided before the bolt or screw can be replaced.
A further and perhaps more serious limitation of both molly bolt type as well as toggle bolt type wall anchors is their relatively low maximum weight loading or applied loading capacity. For example, a serious problem exists in securely mounting heavy weight-bearing or force-loaded hardware on hollow wall constructions, such as grab bars that are mounted next to bathtubs or toilets to assist handicapped persons. The problem existing in field installation of such grab bars is to find adequate support to mount the bars that will sustain a load of about 200 to 300 lbs. Fasteners presently on the market do not meet this requirement.
Moreover, typically the load-bearing structure of the wall anchor structure is the single threaded operating bolt or screw that is utilized to pivot the arms or compress the molly bolt to form holding arms, the head end of this bolt or screw being utilized to support the load to be secured to the wall by the anchor. Thus, these wall anchors are by their nature "single-point" or "single-member" support structure systems with inherently limited load-bearing capability per anchor. Although theoretically a number of anchors could be used to increase the load-bearing capability for a given system, this is often not a practical solution.
Thus, even though there are numerous hollow wall fastening members and anchor structures and systems known and used commercially in the art, there remains a continuing and long felt need for an inexpensive wall anchoring structure and system that provides an economical and reliable support, easy insertion steps, removability with minimal damage to the hollow wall, can be readily manufactured at a low cost yet have a high strength-to-weight ratio and provides a high load-bearing capability for use in reliably mounting grab bars or like heavy-duty hardware on hollow walls, such as drywalls, composition sheet walls, plasterboard walls and molded fiberglass walls.